1. Field of the Invention
The technical field of one embodiment of the invention disclosed in this specification, drawings, and the like relates to an object, a method, or a manufacturing method. Alternatively, it relates to a process, a machine, manufacture, or a composition of matter. Specifically, one embodiment of the invention relates to a semiconductor device and a driving method thereof. More specifically, one embodiment of the invention relates to a programmable logic device and a driving method thereof.
2. Description of the Related Art
An application specific integrated circuit (ASIC) is a circuit in which all circuits are fixed at the time of manufacture, whereas a programmable logic device (hereinafter also referred to as PLD in this specification) is a device that can function with an intended circuit structure set by a user after the shipment. The PLD described in this specification includes all of the following in its category: a simple PLD (SPLD), which is small in the logic scale; a complex PLD (CPLD), which is medium in the logic scale; and a field programmable gate array (FPGA), which is large in the logic scale.
In general, a PLD includes arrayed logic elements (hereinafter also referred to as LE in this specification) and circuits (switches) that control conduction between the LEs. The function of a PLD can be changed by changing the functions of the LEs. In addition, the function of a PLD can also be changed by changing the connection between the LEs with the circuits that control conduction between the LEs.
A circuit that controls conduction between LEs incorporates a configuration memory that can store configuration data.
A PLD having a multi-context function, which incorporates configuration memories that can store plural sets of configuration data and switches a set of configuration data with another set of configuration data during the operation of the PLD, is known. A PLD having the multi-context function performs an operation in accordance with the selected configuration data, and is capable of rewriting non-selected configuration data during the operation, i.e., capable of performing dynamic reconfiguration. A PLD capable of dynamic reconfiguration is disclosed in Patent Document 1 below.